1. Field of the Invention
This invention relates to an electrophotographic image forming member which is sensitive to electromagnetic waves such as light (in the broad sense of the term, the light includes ultraviolet rays, visible light rays, infrared rays, X-rays, .gamma.-rays, and so on).
2. Description of Prior Arts
The photoconductive material to constitute the photoconductive layer of the electrophotographic image forming member is required to have various characteristics such that it possesses high sensitivity, high resistance, and a spectral characteristic which is as close to a luminosity factor as possible, a high light response speed, a large light absorbing coefficient in a visible light region, a high stability against external influences such as light, heat, etc., and, in addition, it gives no harm at all or the least harm to human body during manufacturing and using.
In particular, the harmlessness to the human body is very important, when the photoconductive material forms an integral part of the electrophotographic image forming member to be used with the electrophotographic apparatus as the office machine.
From such standpoint, amorphous silicon (hereinafter abbreviated as "a-Si") has been considered a promising material in recent years. Various patent specifications and other publications disclose electrophotographic image forming members using the a-Si, e.g., U.S. Pat. No. 4,225,222, U.S. Pat. No. 4,265,991 and Japanese patent publication No. 55-69149. The electrophotographic image forming member disclosed in these publications constitutes its photoconductive layer with a so-called amorphous hydrogenated silicon (hereinafter abbreviated as "a-Si:H") containing therein hydrogen atom, dark resistance and photoconductive characteristics of which are largely governed by the quantity of the hydrogen atom and the method of introducing hydrogen atom into the layer. When the a-Si:H layer having good electrical characteristics and photoconductive characteristics for electrophotography is to be formed with good reproducibility, the layer growth should be made slow, which leaves problems in respect of its productivity in the industrialized mass production. For instance, when fabricating the electrophotographic image forming member having characteristics which are usually required, the growth rate of the a-Si:H layer is approximately 1/100 of that in the case of fabricating a layer of selenium, etc. Considering the charge sustaining capability of electrophotographic image forming members and the developing technique at the present stage, the thickness of the photoconductive layer should be at least 10 microns, which causes difficulty in its industrialized mass production. Moreover, as the a-Si:H layer has a large internal stress, when its layer thickness is made thicker than 10 microns or so, it tends to peel off a substrate or create cracks therein as the case may be, on account of which it is said that the layer having a large area is difficult to be formed.